Ratio of viscosity to entropy density in a strongly coupled one-component plasma

TL;DR

This paper investigates the viscosity to entropy density ratio in a strongly coupled one-component plasma, confirming it always exceeds the lower bound predicted by string theory, with the viscosity showing a minimum at intermediate coupling.

Contribution

It demonstrates that the viscosity to entropy density ratio in a strongly coupled plasma remains above the string theory bound and identifies a minimum in viscosity as a function of coupling strength.

Findings

The ratio exceeds the string theory lower bound.

Viscosity shows a minimum at intermediate coupling.

The ratio remains above the theoretical lower limit.

Abstract

String theoretical arguments led to the hypothesis that the ratio of viscosity to entropy of any physical system has a lower bound. Strongly coupled systems usually have a small viscosity compared to weakly coupled plasmas in which the viscosity is proportional to the mean free path. In the case of a one-component plasma the viscosity as a function of the coupling strength shows a minimum. Here we show that the ratio of viscosity to entropy of a strongly coupled one-component plasma is always above the lower bound predicted by string theory.